Recently, research is conducted to develop Silicon Carbide (SiC) devices in many research institutions. As characteristics of the SiC devices, it can be mentioned of low on resistance, high speed switching, high temperature operation, etc.
Conventionally, since an operating range of the Si devices, such as Insulated Gate Bipolar Transistors (IGABTs), currently used in the field of a semiconductor power module was limited to about 150 degrees C., it was possible to drive the Si devices even when using low melting point solder, such as a conventional Sn—Ag alloy based solder.
However, the SiC devices can theoretically operate in temperatures reaching about 400 degrees C. Therefore, if the SiC devices are driven at high temperature when using the conventional low melting point solder, a short circuit between electrodes, a delamination between the SiC device and a base plate, etc. will occur due to fusing of bonding parts where the low melting point solder is used, and thereby compromising reliability of the SiC devices.
Accordingly, the SiC devices could not be driven at high temperature, and therefore the characteristics of the SiC devices were not able to be used.
Nowadays, the bonding under the high temperature melting point has been developed actively. However, taking mass production into consideration, the bonding under the high temperature melting point is not suitable for mass productivity because a period of process time is so long. Since process temperature is also still higher when using the bonding under the high temperature melting point, an excessive stress is applied to materials due to the difference in a coefficient of thermal expansion between individual materials used for fabricating a module, and thereby it cannot secure the reliability of the SiC devices.
It is already disclosed about a method for interconnect between the SiC devices, and a low thermal resistance package (for example, refer to Patent Literature 1 and Patent Literature 2). The Patent Literature 1 and Patent Literature 2 disclose a fabrication method of a package used for housing an SiC device, and also disclose that the SiC device is bonded to other parts or conductive surfaces using Transient Liquid Phase (TLP) bonding technology.
On the other hand, it is already disclosed about a compound solder article whose melting point is comparatively low (e.g., its melting point is not more than 430 degrees C.) including Sn and/or Pb (for example, refer to Patent Literature 3). In Patent Literature 3, the solder alloy has a difference in temperature between the liquid phase and the solid phase smaller than that of the basic solder.
Furthermore, it is already disclosed also about transfer of metal MEMS packages using a wafer-level solder transfer technology (for example, refer to Non Patent Literature 1). In Non Patent Literature 1, a device wafer and a package cap are bonded by the TLP technology using relatively thin Ni—Sn layer.
It is already disclosed also about a liquid cooling device for cooling a semiconductor element via a cooling device from a back side surface of the semiconductor element (for example, refer to Patent Literature 4).